A modified dynamic Lee model for two-phase closed thermosyphon (TPCT) simulation

A modified model consisting of a dynamic Lee model, volume of fluid model, and continuum surface force model is developed. The modified model investigates heat transfer characteristics of the vapor-liquid phase change process and details of the two-phase flow during operation of a two-phase closed thermosyphon. The mass transfer time relaxation parameters for the Lee phase change model are the most critical coefficients which determine the rate of the vapor-liquid phase change. A dynamic adjustment of the mass transfer time relaxation parameters for the Lee phase change model is realized based on the amount of mass transfer between the vapor and liquid phases and the values of the mass transfer time relaxation parameters become stabilized. The relative error between the modified model and experimental data for the temperature distribution is 5%, representing an acceptable agreement. Compared with the original model, the maximum thermal resistance errors in evaporation section and condensation section are reduced by 19.3% and 107.1%, respectively. These results indicate that the modified model can provide good corrections with high accuracy.